Production of acetylene and ethylene by incomplete combustion of hydrocarbons



Apr1l26, 1966 L. LORENZ ETAL 3,248,447

PRODUCTION OF ACETYLENE AND ETHYLENE BY INCOMPLETE COMBUSTION OFHYDROCARBONS Filed Feb. 24, 1964 INVENTORS; LOTHAR LORENZ WALTERTELTSCHIK ATT'YS United States Patent 3 Claims. (51. 260-679) Thisapplication is a continuation-in-part of our copending applicationSerial No. 164,526, filed January 5, 1962, now abandoned.

This invention relates to a process for the production of acetylene andethylene from hydrocarbons. In particular it relates to a process ofthis kind in which an additional amount of hydrocarbons is added to thehot reaction mixture.

It is known that acetylene can be prepared by incomplete combustion ofgaseous or vaporized hydrocarbons with oxygen by separately preheatingthe gases, mixing them while hot and supplying the mixture to a reactionchamber in which cracked gas containing acetylene is formed by partialcombustion of the hydrocarbons. The cracked gas, after leaving thereaction chamber, is cooled by means of a coolant to temperatures below100 C., the coolant beingheat'ed up and vaporized. The initial materialsused in the prior art methods are hydrocarbons with one to ten carbonatoms in the molecule, and oxygen or gas containing oxygen, the weightratio of hydrocarbon to oxygen being about 1:1. The gaseous initialmaterials are preheated to about 150 to 700 C. prior to the reaction.

A method for carrying out chemical reactions at high temperatures isalso known in which hydrocarbons are added to hot, completely burntcombustion gases. This method has the disadvantage that the cracked gasis diluted by the completely burnt combustion gas so that separation ofacetylene or, ethylene from the said gas is rendered difficult.

In the production of acetylene and o lefine-s from gaseous or vapo'roushydrocarbons by leading them through spaces heated to high temperaturesor through electric arcs and quenching the reaction mixture by injectingliquids, it is also known to add to the hot gas mixture, prior toquenching and immediately behind the zone of maximum temperature orafter the production of acetylene, hydrocarbons in an amountinsufiicient for quenching. The amount of carbon black formed during theproduction of acetylene is only slightly aiiected by this measure.

It is an object of the present invention to provide a process for theproduction of acetylene and ethylene in which the ratio of acetylene toethylene may be varied at random. Another object is the production ofacetylene with reduced carbon black formation. A fiurther object of theinvention is the production of acetylene with a low consumption ofhydrocarbons and oxygen.

In accordance with our invention these objects are achieved, i.e.acetylene and ethylene are produced by incomplete combustion ofhydrocarbons with oxygen or an oxygen-containing gas in a reaction zonein which a maximum temperature of about 1300 to 1650 C. normallyprevails and quenching the hot combustion gas with a cooling liquid byintroducing an amount of hydrocarbon into the first 'half of thereaction zone, in addition to the reaction mixture of hydrocarbon andoxygen-containing g-as during its passage through 3,248,447 PatentedApr. 26, 1966 the reaction zone, the said additional amount ofhydrocarbon being fed into the reaction zone ahead of the point atwhich, had the additional feed not been made, the normal maximumtemperature would occur, the said additional feed of hydrocarbons beingmade in such an amount that the maximum temperature of the reaction gasis reduced to 500 to 1200 C.

The term reaction zone as used in this specification denotes that partof the reactor which extends from the point where the flame begins andthe point where the flame reaction is stopped by quenching with acoolant.

The materials used in the practice of our invention are hydrocarbonshaving one to ten carbon atoms and oxygen or gases containing oxygen.When these gases are reacted in the reaction chamber without an additionof other hydrocarbons being made, a maximum temperature of about 1300 to1650 C. occurs. The reaction period is about 2/1000 to of a second. Thebydrocarbons to be used as an additive to the reaction mixture are thosethaving two to twelve carbon atoms. They are used in a liquid orvaporous form in an amount of from about'10 to by weight, percentagewith reference to the weight of the reaction mixture. The additionis'made in the region behind the zone in which the gas mixture isignited.

When no additional feed of hydrocarbon is made, the zone of maximumtemperature is at the end of the reaction chamber slightly ahead of thepoint where the coolant, for example water, with which the hot gas isquenched, is injected. When an additional feed of hydrocarbon is made,the temperature does not rise to its maximum height, but rather drops toabout 500 to 1200 C. in that zone of the reaction chamber where themaximum temperature would occur if the additional feed of hydrocarbonwas not made.

The oxygen content of the reaction mixture is about 30% by volume aheadof the point Where partial combustion begins. After ignition the oxygencontent of the gas mixture decreases as the combustion advances, theadditional feed of hydrocarbon being injected in the first half of thereaction zone, where the oxygen content is from 1 to 10% by volume. Inthe practice of our invention it is preferred to inject the additionalhydrocarbon feed at the point where the oxygen content is from 2 to 5%by volume.

The advantage of the process according to this invention over similarprior art processes lies in the fact that the content of carbon black inthe cracked gas is greatly decreased, so that purification of thecracked gas is simplified. The hydrocarbons to be added to the mixtureof the reaction gases should preferably be used in such an amount thatthe reaction mixture is cooled to about 500 to 1200 C. as the yield ofacetylene and ethylene is highest in this case. We have found that thecomposition of the cracked gas is dependent not only on the amount ofhydrocarbons added to the reaction mixture but also on the distance atwhich the point of feed is arranged ahead of the zone of maximumtemperature in the reaction chamber in which the partial combustion ofthe hydrocarbon takes place. If the additional feed of hydrocarbonintroduced into the cracked gas in the first half of the reaction zone,the yield of ethylene is higher as compared with an addition ofhydrocarbon in the second half of the reaction zone. The content ofcarbon black in the cracked gas falls to half the content of a crackedgas obtained by adding the hydrocarbons into the second half of thereaction zone.

The following example, given with reference to the accompanyingdiagrammatic drawing, .will further illustrate the invention withoutlimiting it.

3 EXAMPLE Referring to the drawing, A is a reaction chamber in whichpartial combustion of hydrocarbons takes place in conventional manner.In thisembodiment injection nozzles B and D are provided in the firstand second half of the reaction zone for the addition of furtherhydrocarbon. Cracked gas leaving the reaction chamber is quenched inconventional manner by a coolant, for example, water supplied from jetsC.

25 kilograms per hour of light gasoline (boiling point oxygen are heatedup in separate preheaters to 320 0, mixed in a mixer, supplied to thereaction chamber A and reacted therein. The hot reaction gas is quenchedwith water at C at the end of the reaction chamber.

In a first and a second experiment carried out under otherwise identicalconditions, 10.7 kilograms of light gasoline (boiling point 30 to 100C.) is fed per hour through nozzle B into the first half of the reactionzone (Experiment I) and, in accordance with one of the prior artmethods, into the second half of the reaction zone through nozzle D(Experiment II).

The results shown in the following table are obtained:

Table Acetylene content in cracked gas in percent 6. 6 Ethylene contentin cracked gas in percent (3. 1 Content of carbon black in cracked gasg./m. (S.T.P.) 2 9 From a comparison of the results in column I whichcorresponds to Experiment I with those in column 11 which corresponds toExperiment II it will be apparent that a higher percentage of ethyleneand a markedly lower percentage of carbon black are obtained inExperiment I.

What we claim is:

1. In a process for the production of acetylene and 30 to 100 0. and15.6 m. (S.T.P.) per hour of ethylene by incomplete combustion ofhydrocarbons with an oxygen-containing gas and quenching the hotcombustion gases with a coolant, said incomplete combustion beingcarried out in a reaction zone in which a maximum temperature of about1300 C. to 1650 C. normally prevails, the improvement for substantiallyreducing the formation of carbon black which comprises: introducing anamount of hydrocarbon into the first half of the reaction zone inaddition to the reaction mixture of hydrocarbon and oxygen-containinggas during its passage through said reaction zone, said additionalamount of hydrocarbon being fed into the the reaction zone ahead of thepoint at which, had the additional feed not been made, said normalmaximum temperature would occur, the said additional feed of hydrocarbonbeing made in such an amount that the maximum temperature of thereaction gas is reduced to 500 to 1200 C.

2. A process as claimed in claim 1 wherein said additional feed ofhydrocarbon is about 10 to by weight with reference to the weight of thereaction gas at the point where it is introduced. 3. A process asclaimed in claim 1 wherein hydrocarbons having 1 to 10 carbon atoms inthe molecule are employed for the initial combustion and hydrocarbonshaving 2 to 12 carbon atoms are employed for said addition.

References Cited by the Examiner UNITED STATES PATENTS 5/1961 Pechtoldet al. 260679 7/1964 Fauser 260679 OTHER REFERENCES ALPHONSO D.SULLIVAN, Primary Examiner;

1. IN A PROCESS FOR THE PRODUCTION OF ACETYLENE AND ETHYLENE BYINCOMPLETE COMBUSION OF HYDROCARBONS WITH AN OXYGEN-CONTAINING GAS ANDQUENCHING THE HOT COMBUSTION GASES WITH A COOLANT, SAID INCOMPLETECOMBUSTION BEING CARRIED OUT IN A REACTION ZONE IN WHICH A MAXIMUMTEMPERATURE OF ABOUT 1300C. TO 1650*C. NORMALLY PREVAILS, THEIMPROVEMENT FOR SUBSTANTIALLY REDUCING THE FORMATION OF CARBON BLACKWHICH COMPRISES: INTRODUCING AN AMOUNT OF HYDROCARBON INTO THE FIRSTHALF OF THE REACTION ZONE IN ADDITION TO THE REACTION MIXTURE OFHYDROCARBON AND OXYGEN-CONTAINING GAS DRUING ITS PASSAGE THROUGH SAIDREACTION ZONE, SAID ADDITIONAL AMOUNT OF HYDROCARBON BEING FED INTO THEREACTION ZONE AHEAD OF THE POINT AT WHICH, HAD THE ADDITIONAL FEED NOTBEEN MADE, SAID NORMAL MAXIMUM TEMPERATURE WOULD OCCUR, THE SAIDADDITIONAL FEED OF HYDROCARBON BEING MADE IN SUCH AN AMOUNT THAT THEMAXIMUM TEMPERATURE OF THE REACTION GAS IN REDUCED TO 500* TO 1200*C.